1. Field of the Invention
The present invention relates to a method of manufacturing a stacked semiconductor device and, particularly, to a method of manufacturing a stacked semiconductor device in which a semiconductor device body such as an IC (Integrated Circuit) is mounted on a substrate.
2. Description of the Background Art
A stacked semiconductor device realizing multiple functions by itself by stacking a plurality of semiconductor device bodies such as ICs of different functions on a substrate and connecting the semiconductor device bodies to each other has been proposed.
An example is a stacked semiconductor device in which a logic IC is mounted as a semiconductor device body in the first stage on a substrate and a memory IC is mounted as a semiconductor device body in the second stage on the logic IC.
In such a stacked semiconductor device, an external lead for the semiconductor device body in the second stage is soldered to a land of the substrate on which the semiconductor device body in the first stage is mounted.
As a conventional method of soldering an external lead for a semiconductor device body to a land, a soldering method disclosed in Japanese Patent Laying-Open No. 5-258986 will be described.
First, a pallet without a solder chip in which an initial semiconductor device body on which a solder chip is not yet applied is housed is prepared. On the other hand, a pallet with a chip having a groove in which a solder paste is to be applied is prepared.
A solder paste is applied on the pallet with the chip. The groove is filled with the applied solder paste with a squeegee.
Subsequently, the semiconductor device body is taken out from the pallet without a solder chip. The taken semiconductor device body is mounted on the pallet with the chip so that the outer lead of the semiconductor device body is positioned on the groove of the pallet with the chip.
In a state where the semiconductor device body is mounted on the pallet with the chip, the pallet with the chip is heated to a predetermined temperature. The semiconductor device body is pressed and the external lead enters the solder paste.
The solder paste is heated to thereby become a solder metal and is adhered to the external lead. The semiconductor device body to which the solder is supplied to the external lead is soldered to a predetermined substrate and is mounted.
However, the conventional method has the following problems. As described above, the solder is supplied to the external lead of the semiconductor device body by pushing the external lead into the solder filled in the groove in the pallet with the chip.
At the time of bringing the semiconductor device body up, the solder filled in the groove is attached to the external lead by an adhesion force to the external lead. At this time, depending on the way of pushing the external lead into the solder, the adhesion force of the solder to the external lead varies and, there is a case that the amount of solder adhered to the external lead becomes uniform.
Consequently, for example, at the time of bonding the external lead of the semiconductor device body in the second stage to the land, soldering is not conducted securely, and there is a case that the semiconductor device in the first stage and the semiconductor device in the second stage are not electrically connected excellently. As a result, a problem such that a desired function of the semiconductor device cannot be assured might occur.